1. Field of Invention
This invention relates to a reactor for gasifying granular fuels, particularly coal, under a pressure of 5 to 150 bars by a treatment with gasifying agents which contain free oxygen, steam and/or carbon dioxide, wherein the fuel forms in the reactor a fixed bed, which is gradually descending, the gasifying agents are introduced into the fixed bed from below, the incombustible mineral constituents of the fuel are withdrawn below the fixed bed as solid ash or liquid slag, and the fixed bed contains at least one stirring arm, which is rotatable about a vertical axis and is approximately triangular in cross-section and has a knife edge penetrating through the coal bed and a rear crushing edge.
2. Discussion of Prior Art
Such a stirrer is known from German Pat. No. 23 53 241 and from the corresponding U.S. Pat. No. 3,951,616. German Patent Publication No. 10 21 116 also shows a reactor having a stirring arm. The gasification of solid fuels is known and disclosed, e.g., in Ullmanns Encyklopadie der technischen Chemie, 4th edition (1977), Volume 14, on pages 383 to 386. Details of the gasification involving a formation of solid ash are apparent from U.S. Pat. Nos. 3,540,867 and 3,854,895. The modification of the process involving a formation of liquid slag has been explained in British Patent Specifications Nos. 1,507,905; 1,508,771 and 1,512,677.
The fuel which is suitable for the reactor usually consists of non-caking, swellable or caking coal although other carbonaceous materials, such as wood, peat or biomass can also be gasified. The granular fuel has a particle size in the range of about 3 to 60 mm so that the fixed bed is adequately permeable to gas. It is known to loosen the fixed bed by means of a stirrer having one or more stirring arms in order to improve the permeability to gas.